The present invention is related to a pump-attached dipole electro-plating barrel for use in electro-plating process.
In conventional horizontal rotary plating techniques, a barrel is used for depositing a coating of metal on by electrode. In a variety of contactor of electrode, such as centerod type, dangler contact type, side contact type, grid contact type, or bottom contact type, a satisfactory performance is still difficult to achieve.
According to conventional methods, slinder working pieces tend to be obstructed and bent by the lead wires or center rod in a rotary barrel during tumbling of operation or unloading. Besides, because the area of contractor of cathode is restricted, the working pieces to be plated will get a high gradient in the distribution of thickness. Further, the contactor of cathode of a conventional electro-plating barrel may be gradually built-up due to operation for a period.
In the bottom contact type, high gradient in the distribution of thickness may be eliminated. But because the electrodes in a rotary barrel are connected in parallel and simultaneously charged with negative electricity, and the working pieces generally fall to the bottom area inside the barrel during electro-plating operation, the electrodes which are turned to an upper position spaced from the working pieces below may cause a phenomenon of ultra high current density. As a consequence of such an ultra high current density, burnt deposit forms around the electrodes and will interfere with the operation of electro-plating process. Therefore, the electrodes must be periodically replaced with new ones or well treated to remove the build-up layer therefrom. It is indeed very troublesome to dismount the electrodes from an electro-plating barrel. During cleaning process, certain tools or chemicals may be required. Further, the build-up on electrode simultaneously increases the consumption of anode metal or metal ion in bath. Also in the bottom contact type, electro-plating solution level may be adjusted during electro-plating process and the upper raws of electrode may be left from the plating bath, to reduce possible depositing of metal complex on the electrodes. In fact, not only the difficulty in controlling the bath level, but also the air being compressed into the electro-plating solution, certain type of electro-plating solutions is not suitable for such operation. For example, anaerobic electro-plating solution (cyanide solution or tin sulfite solution) is not suitable for use in bath level controlling process.
In comparison with rack plating, the conventional horizontal electro-plating rotary barrel is relatively inferior in performance since the circulation of outside electro-plating solution with inner electro-plating solution is interfered and the current path between the anode and cathod is obstructed. Regular horizontal electro-plating rotary barrel is generally made of plastic sheet perforated with small holes or relatively bigger holes linned with mesh clothes to prevent from dropping of working pieces during electro-plating process. However, the holes made on the barrel are not sufficient enough so that good circulation of electro-plating solution can not be well performed through the barrel. As a consequence of poor circulation of electro-plating solution and poor current efficiency high quality of electro-plating effect can not be achieved.
Therefore, the main object of the present invention is to provide such a pump-attached dipole electro-plating barrel which can automatically electrolyze any metal which deposited on the electrodes so as to minimize the consumption of anode metal or metal ions in bath.
Another object of the present invention is to provide such a pump-attached dipole electro-plating barrel which utilizes a flexible impellar vane pump to constantly pump outside plating solution into the barrel so as to equalize the concentration of the plating solution internally as well as externally.